Commit 7e9f735e authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: x86: Apply TSX_CTRL_CPUID_CLEAR if and only if the vCPU has RTM or HLE 



When emulating CPUID, retrieve MSR_IA32_TSX_CTRL.TSX_CTRL_CPUID_CLEAR if
and only if RTM and/or HLE feature bits need to be cleared.  Getting the
MSR value is unnecessary if neither bit is set, and avoiding the lookup
saves ~80 cycles for vCPUs without RTM or HLE.

Cc: Jim Mattson <jmattson@google.com>
Reviewed-by: default avatarJim Mattson <jmattson@google.com>
Link: https://lore.kernel.org/r/20241211013302.1347853-4-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent aa93b6f9

arch/x86/kvm/cpuid.c

+2 −1
Original line number Diff line number Diff line
@@ -1999,7 +1999,8 @@ bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, 
		*edx = entry->edx;

		if (function == 7 && index == 0) {

			u64 data;

		        if (!__kvm_get_msr(vcpu, MSR_IA32_TSX_CTRL, &data, true) &&

			if ((*ebx & (feature_bit(RTM) | feature_bit(HLE))) &&

			    !__kvm_get_msr(vcpu, MSR_IA32_TSX_CTRL, &data, true) &&

			    (data & TSX_CTRL_CPUID_CLEAR))

				*ebx &= ~(feature_bit(RTM) | feature_bit(HLE));

		} else if (function == 0x80000007) {